At this point, La Voix and Balvinder recurring in the bottom two is going to be inevitable.
In terms of who else joins them, I actually think it could be ANYONE with the exception of perhaps Vicky. Amber's already demonstrated a lack of public support, and I actually suspect Lewis could easily suffer the same issue in a bad week. Alex and Karen will likely live and die by their scores in any given week. George is a total wildcard - I know the prevailing wisdom is his online fanbase will see him through, but I also suspect that might also make him a judges target in any dance-off; do they really risk him undermining the whole series by winning the damn thing given his middling performance thus far?